<?php
class Arm_Controller_Plugin_Install extends Zend_Controller_Plugin_Abstract
{
    public function preDispatch(Zend_Controller_Request_Abstract $request)
    {
     if($request->getModuleName() !== 'install') {   
     $request->setModuleName('install');
     $request->setControllerName('index');
     $request->setActionName('index');
     }
     return $request;
    }
     
}